scholarly journals N-terminal degradation activates the Nlrp1b inflammasome

2018 ◽  
Author(s):  
Ashley J. Chui ◽  
Marian C. Okondo ◽  
Sahana D. Rao ◽  
Kuo Gai ◽  
Andrew R. Griswold ◽  
...  
Keyword(s):  
Cell Death ◽  
Lethal Factor ◽  
Proteasomal Degradation ◽  
Degradation Pathway ◽  
Common Mechanism ◽  
Caspase 1 ◽  
C Terminus ◽  
Anthrax Lethal Factor ◽  
N Terminus ◽  
Inflammatory Caspases

AbstractIntracellular pathogens and danger signals trigger the formation of inflammasomes, which activate inflammatory caspases and induce pyroptotic cell death. The anthrax lethal factor metalloprotease and small molecule DPP8/9 inhibitors both activate the Nlrp1b inflammasome, but the molecular mechanism of Nlrp1b activation is not known. Here, we used genome-wide CRISPR/Cas9 knockout screens to identify genes required for Nlrp1b-mediated pyroptosis, and discovered that lethal factor induces cell deathviathe N-end rule proteasomal degradation pathway. Lethal factor directly cleaves Nlrp1b, which induces the N-end rule-mediated degradation of the Nlrp1b N-terminus and thereby frees the Nlrp1b C-terminus to activate caspase-1. DPP8/9 inhibitors also induce proteasomal degradation of the Nlrp1b N-terminus, but, in contrast, not through the N-end rule pathway. Overall, these data reveal that N-terminal degradation is the common mechanism for activation of this innate immune sensor protein.One Sentence SummaryProteasome-mediated degradation of the Nlrp1b N-terminus releases the Nlrp1b C-terminus to activate caspase-1 and induce pyroptotic cell death.

scholarly journals N-terminal degradation activates the NLRP1B inflammasome

Science ◽  
2019 ◽  
Vol 364 (6435) ◽  
pp. 82-85 ◽  
Author(s):  
Ashley J. Chui ◽  
Marian C. Okondo ◽  
Sahana D. Rao ◽  
Kuo Gai ◽  
Andrew R. Griswold ◽  
...  
Keyword(s):  
Lethal Factor ◽  
Proteasomal Degradation ◽  
Degradation Pathway ◽  
Activation Mechanism ◽  
C Terminus ◽  
Anthrax Lethal Factor ◽  
Genome Wide ◽  
N Terminus ◽  
The Common ◽  
Inflammatory Caspases

Intracellular pathogens and danger signals trigger the formation of inflammasomes, which activate inflammatory caspases and induce pyroptosis. The anthrax lethal factor metalloprotease and small-molecule DPP8/9 inhibitors both activate the NLRP1B inflammasome, but the molecular mechanism of NLRP1B activation is unknown. In this study, we used genome-wide CRISPR-Cas9 knockout screens to identify genes required for NLRP1B-mediated pyroptosis. We discovered that lethal factor induces cell death via the N-end rule proteasomal degradation pathway. Lethal factor directly cleaves NLRP1B, inducing the N-end rule–mediated degradation of the NLRP1B N terminus and freeing the NLRP1B C terminus to activate caspase-1. DPP8/9 inhibitors also induce proteasomal degradation of the NLRP1B N terminus but not via the N-end rule pathway. Thus, N-terminal degradation is the common activation mechanism of this innate immune sensor.

scholarly journals A Type III Effector NleF from EHEC Inhibits Epithelial Inflammatory Cell Death by Targeting Caspase-4

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Ting Song ◽  
Kaiwu Li ◽  
Wei Zhou ◽  
Jing Zhou ◽  
Yuan Jin ◽  
...  
Keyword(s):  
Cell Death ◽  
Inflammatory Cell ◽  
Gastrointestinal Disease ◽  
Highly Pathogenic ◽  
E Coli ◽  
Caspase 1 ◽  
T3ss Effector ◽  
Inflammatory Caspases ◽  
Epithelial Cell Death ◽  
Host Inflammatory Response

EnterohemorrhagicE. coli(EHEC) is a highly pathogenic bacterial strain capable of inducing severe gastrointestinal disease. Here, we show that EHEC uses the T3SS effector NleF to counteract the host inflammatory response by dampening caspase-4-mediated inflammatory epithelial cell death and by preventing the production of IL-1β. The other two inflammatory caspases, caspase-1 and caspase-5, are not involved in EHEC ΔnleF-induced inflammatory cell death. We found that NleF not only interrupted the heterodimerization of caspase-4-p19 and caspase-4-p10, but also inhibited the interaction of caspase-1 and caspase-4. The last four amino acids of the NleF carboxy terminus are essential in inhibiting caspase-4-dependent inflammatory cell death.

Anthrax Lethal Factor Cleaves the N-Terminus of MAPKKs and Induces Tyrosine/Threonine Phosphorylation of MAPKs in Cultured Macrophages

1998 ◽  
Vol 248 (3) ◽  
pp. 706-711 ◽  
Author(s):  
Gaetano Vitale ◽  
Rossella Pellizzari ◽  
Chiara Recchi ◽  
Giorgio Napolitani ◽  
Michèle Mock ◽  
...  
Keyword(s):  
Lethal Factor ◽  
Anthrax Lethal Factor ◽  
N Terminus

scholarly journals Interactions between the N- and C-termini of the mechanosensitive ion channel AtMSL10 are consistent with a three-step mechanism for activation

2020 ◽  
Vol 71 (14) ◽  
pp. 4020-4032 ◽  
Author(s):  
Debarati Basu ◽  
Jennette M Shoots ◽  
Elizabeth S Haswell
Keyword(s):  
Cell Death ◽  
Ion Channel ◽  
Conformational Changes ◽  
Molecular Mechanisms ◽  
Fluorescent Protein ◽  
Adaptive Responses ◽  
C Terminus ◽  
N Terminus ◽  
Mechanosensitive Ion Channel ◽  
Green Fluorescent

Abstract Although a growing number of mechanosensitive ion channels are being identified in plant systems, the molecular mechanisms by which they function are still under investigation. Overexpression of the mechanosensitive ion channel MSL (MscS-Like)10 fused to green fluorescent protein (GFP) triggers a number of developmental and cellular phenotypes including the induction of cell death, and this function is influenced by seven phosphorylation sites in its soluble N-terminus. Here, we show that these and other phenotypes required neither overexpression nor a tag, and could also be induced by a previously identified point mutation in the soluble C-terminus (S640L). The promotion of cell death and hyperaccumulation of H2O2 in 35S:MSL10S640L-GFP overexpression lines was suppressed by N-terminal phosphomimetic substitutions, and the soluble N- and C-terminal domains of MSL10 physically interacted. We propose a three-step model by which tension-induced conformational changes in the C-terminus could be transmitted to the N-terminus, leading to its dephosphorylation and the induction of adaptive responses. Taken together, this work expands our understanding of the molecular mechanisms of mechanotransduction in plants.

scholarly journals The Impact of Autophagy on Cell Death Modalities

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Stefan W. Ryter ◽  
Kenji Mizumura ◽  
Augustine M. K. Choi
Keyword(s):  
Cell Death ◽  
Inflammatory Responses ◽  
Degradation Pathway ◽  
Therapeutic Interventions ◽  
Caspase 1 ◽  
Regulated Cell Death ◽  
Caspase Inhibition ◽  
Autophagic Degradation ◽  
Dependent Cell ◽  
The Impact

Autophagy represents a homeostatic cellular mechanism for the turnover of organelles and proteins, through a lysosome-dependent degradation pathway. During starvation, autophagy facilitates cell survival through the recycling of metabolic precursors. Additionally, autophagy can modulate other vital processes such as programmed cell death (e.g., apoptosis), inflammation, and adaptive immune mechanisms and thereby influence disease pathogenesis. Selective pathways can target distinct cargoes (e.g., mitochondria and proteins) for autophagic degradation. At present, the causal relationship between autophagy and various forms of regulated or nonregulated cell death remains unclear. Autophagy can occur in association with necrosis-like cell death triggered by caspase inhibition. Autophagy and apoptosis have been shown to be coincident or antagonistic, depending on experimental context, and share cross-talk between signal transduction elements. Autophagy may modulate the outcome of other regulated forms of cell death such as necroptosis. Recent advances suggest that autophagy can dampen inflammatory responses, including inflammasome-dependent caspase-1 activation and maturation of proinflammatory cytokines. Autophagy may also act as regulator of caspase-1 dependent cell death (pyroptosis). Strategies aimed at modulating autophagy may lead to therapeutic interventions for diseases in which apoptosis or other forms of regulated cell death may play a cardinal role.

scholarly journals DPP9 directly sequesters the NLRP1 C-terminus to repress inflammasome activation

2020 ◽  
Author(s):  
L. Robert Hollingsworth ◽  
Humayun Sharif ◽  
Andrew R. Griswold ◽  
Pietro Fontana ◽  
Julian Mintseris ◽  
...  
Keyword(s):  
Cell Death ◽  
Active Site ◽  
Protein Turnover ◽  
Ternary Complex ◽  
Inflammatory Diseases ◽  
Inflammasome Activation ◽  
Terminal Fragment ◽  
C Terminus ◽  
N Terminus ◽  
Dipeptidyl Peptidases

AbstractNLRP1 is a cytosolic inflammasome sensor that mediates activation of caspase-1, which in turn induces cytokine maturation and pyroptotic cell death1-6. Gain-of-function NLPR1 mutations cause skin inflammatory diseases including carcinoma, keratosis, and papillomatosis7-14. NLRP1 contains a unique function-to-find domain (FIIND) that autoproteolyzes into noncovalently associated subdomains15-18. Proteasomal degradation of the autoinhibitory N-terminal fragment (NT) activates NLRP1 by releasing the inflammatory C-terminal fragment (CT)19,20. Cytosolic dipeptidyl peptidases 8 and 9 (DPP8/9) interact with NLRP1, and small-molecule DPP8/9 inhibitors activate NLRP1 by poorly characterized mechanisms11,19,21. Here, we report cryo-EM structures of the human NLRP1-DPP9 complex, alone and in complex with the DPP8/9 inhibitor Val-boroPro (VbP). Surprisingly, the NLRP1-DPP9 complex is a ternary complex comprised of DPP9, one intact FIIND of a non-degraded full-length NLRP1 (NLRP1-FL) and one NLRP1-CT freed by NT degradation. The N-terminus of the NLRP1-CT unfolds and inserts into the DPP9 active site but is not cleaved by DPP9, and this binding is disrupted by VbP. Structure-based mutagenesis reveals that the binding of NLRP1-CT to DPP9 requires NLRP1-FL and vice versa, and inflammasome activation by ectopic NLRP1-CT expression is rescued by co-expressing autoproteolysis-deficient NLRP1-FL. Collectively, these data indicate that DPP9 functions as a “bomb-diffuser” to prevent NLRP1-CTs from inducing inflammation during homeostatic protein turnover.

scholarly journals Human caspase-4 mediates noncanonical inflammasome activation against gram-negative bacterial pathogens

2015 ◽  
Vol 112 (21) ◽  
pp. 6688-6693 ◽  
Author(s):  
Cierra N. Casson ◽  
Janet Yu ◽  
Valeria M. Reyes ◽  
Frances O. Taschuk ◽  
Anjana Yadav ◽  
...  
Keyword(s):  
Cell Death ◽  
Bacterial Pathogens ◽  
Inflammasome Activation ◽  
Gram Negative Bacteria ◽  
Secretion Systems ◽  
Gram Negative ◽  
Human Macrophages ◽  
Caspase 1 ◽  
Inflammatory Caspases ◽  
Human Caspase

Inflammasomes are critical for host defense against bacterial pathogens. In murine macrophages infected by gram-negative bacteria, the canonical inflammasome activates caspase-1 to mediate pyroptotic cell death and release of IL-1 family cytokines. Additionally, a noncanonical inflammasome controlled by caspase-11 induces cell death and IL-1 release. However, humans do not encode caspase-11. Instead, humans encode two putative orthologs: caspase-4 and caspase-5. Whether either ortholog functions similar to caspase-11 is poorly defined. Therefore, we sought to define the inflammatory caspases in primary human macrophages that regulate inflammasome responses to gram-negative bacteria. We find that human macrophages activate inflammasomes specifically in response to diverse gram-negative bacterial pathogens that introduce bacterial products into the host cytosol using specialized secretion systems. In primary human macrophages, IL-1β secretion requires the caspase-1 inflammasome, whereas IL-1α release and cell death are caspase-1–independent. Instead, caspase-4 mediates IL-1α release and cell death. Our findings implicate human caspase-4 as a critical regulator of noncanonical inflammasome activation that initiates defense against bacterial pathogens in primary human macrophages.

Anthrax lethal factor cleaves the N-terminus of MAPKKS and induces tyrosine/threonine phosphorylation of MAPKS in cultured macrophages

1999 ◽  
Vol 87 (2) ◽  
pp. 288-288 ◽  
Author(s):  
G. Vitale ◽  
R. Pellizzari ◽  
C. Recchi ◽  
G. Napolitani ◽  
M. Mock ◽  
...  
Keyword(s):  
Lethal Factor ◽  
Anthrax Lethal Factor ◽  
N Terminus

scholarly journals Interactions between the N- and C- termini of mechanosensitive ion channel AtMSL10 are consistent with a three-step mechanism for activation

2019 ◽  
Author(s):  
Debarati Basu ◽  
Jennette M. Shoots ◽  
Elizabeth S. Haswell
Keyword(s):  
Cell Death ◽  
Ion Channel ◽  
Conformational Changes ◽  
Molecular Mechanisms ◽  
Adaptive Responses ◽  
C Terminus ◽  
Step Model ◽  
N Terminus ◽  
Mechanosensitive Ion Channel ◽  
Cellular Phenotypes

ABSTRACTAlthough a growing number of mechanosensitive ion channels are being identified in plant systems, the molecular mechanisms by which they function are still under investigation. Overexpression of the mechanosensitive ion channel MSL (MscS-Like)10 fused to GFP triggers a number of developmental and cellular phenotypes including the induction of cell death, and this function is influenced by seven phosphorylation sites in its soluble N-terminus. Here, we show that these and other phenotypes required neither overexpression nor a tag and could be also induced by a previously identified point mutation in the soluble C-terminus (S640L). The promotion of cell death and hyperaccumulation of H2O2 in 35S:MSL10S640L-GFP overexpression lines was suppressed by N-terminal phosphomimetic substitutions, and the soluble N- and C-terminal domains of MSL10 physically interacted. We propose a three-step model by which tension-induced conformational changes in the C-terminus are transmitted to the N-terminus, leading to its dephosphorylation and the induction of adaptive responses. Taken together, this work expands our understanding of the molecular mechanisms of mechanotransduction in plants.HIGHLIGHTCell death is triggered by mutations in either the cytoplasmic N- or C-terminus of AìMSLlü. Our proposed model explains how membrane tension may activate signaling through the interaction of these two domains.

scholarly journals Mechanism of gasdermin D recognition by inflammatory caspases and their inhibition by a gasdermin D-derived peptide inhibitor

2018 ◽  
Vol 115 (26) ◽  
pp. 6792-6797 ◽  
Author(s):  
Jie Yang ◽  
Zhonghua Liu ◽  
Chuanping Wang ◽  
Rui Yang ◽  
Joseph K. Rathkey ◽  
...  
Keyword(s):  
Cell Death ◽  
Conformational Changes ◽  
Molecular Mechanisms ◽  
Membrane Lipids ◽  
Enzyme Inhibitor ◽  
Apoptotic Cell ◽  
Specific Inhibitor ◽  
Caspase 1 ◽  
Inflammatory Caspases

The inflammasomes are signaling platforms that promote the activation of inflammatory caspases such as caspases-1, -4, -5, and -11. Recent studies identified gasdermin D (GSDMD) as an effector for pyroptosis downstream of the inflammasome signaling pathways. Cleavage of GSDMD by inflammatory caspases allows its N-terminal domain to associate with membrane lipids and form pores that induce pyroptotic cell death. Despite the important role of GSDMD in pyroptosis, the molecular mechanisms of GSDMD recognition and cleavage by inflammatory caspases that trigger pyroptosis are poorly understood. Here, we demonstrate that the catalytic domains of inflammatory caspases can directly bind to both the full-length GSDMD and its cleavage site peptide, FLTD. A GSDMD-derived inhibitor,N-acetyl-Phe-Leu-Thr-Asp-chloromethylketone (Ac-FLTD-CMK), inhibits GSDMD cleavage by caspases-1, -4, -5, and -11 in vitro, suppresses pyroptosis downstream of both canonical and noncanonical inflammasomes, as well as reduces IL-1β release following activation of the NLRP3 inflammasome in macrophages. By contrast, the inhibitor does not target caspase-3 or apoptotic cell death, suggesting that Ac-FLTD-CMK is a specific inhibitor for inflammatory caspases. Crystal structure of caspase-1 in complex with Ac-FLTD-CMK reveals extensive enzyme–inhibitor interactions involving both hydrogen bonds and hydrophobic contacts. Comparison with other caspase-1 structures demonstrates drastic conformational changes at the four active-site loops that assemble the catalytic groove. The present study not only contributes to our understanding of GSDMD recognition by inflammatory caspases but also reports a specific inhibitor for these caspases that can serve as a tool for investigating inflammasome signaling.

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